Organometallic compounds and purification of such organometallic compounds

ABSTRACT

Disclosed herein are methods of purifying compounds useful for the deposition of high purity tin oxide and high purity compounds purified by those methods. Such compounds are those of the Formula as follows Rx—Sn-A4-x,wherein:A is selected from the group consisting of (YaR′z) and a 3- to 7-membered N-containing heterocyclic group;each R group is independently selected from the group consisting of an alkyl or aryl group having from 1 to 10 carbon atoms;each R′ group is independently selected from the group consisting of an alkyl, acyl or aryl group having from 1 to 10 carbon atoms;x is an integer from 0 to 4;a is an integer from 0 to 1;Y is selected from the group consisting of N, O, S, and P; andz is 1 when Y is O, S or when Y is absent and z is 2 when Y is N or P.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a Divisional of copending application Ser. No.16/442,930, filed Jun. 17, 2019, which is a Continuation of PCTInternational Patent Application No. PCT/CA2018/050933 filed Jul. 31,2018, which claims priority to Canadian Application No. 2975104 filedAug. 2, 2017, all of which are incorporated by reference in theirentireties.

TECHNICAL FIELD

The disclosure relates to organometallic compounds useful for thedeposition of high purity tin oxide and to the purification of suchorganometallic compounds.

BACKGROUND

The semiconductor industry is producing more and more components havingsmaller and smaller feature sizes. The production of such semiconductordevices reveals new design and manufacturing challenges which must beaddressed in order to maintain or improve semiconductor deviceperformance. The production of semiconductor wiring stacks with highdensity, high yield, good signal integrity as well as suitable powerdelivery also presents challenges.

Lithography is a critical pattern transfer technique widely used in thefabrication of a variety of electronic devices which containmicrostructures, such as semiconductor devices and liquid crystaldevices. As device structures are miniaturized, masking patterns used inthe lithography process must be optimized to accurately transferpatterns to the underlying layers.

Multiple-pattern lithography represents a class of technologiesdeveloped for photolithography in order to enhance the feature densityof semiconductor devices. Double-patterning, a subset ofmultiple-patterning, employs multiple masks and photolithographic stepsto create a particular level of a semiconductor device. With benefitssuch as tighter pitches and narrower wires, double-patterning altersrelationships between variables related to semiconductor device wiringand wire quality to sustain performance.

Recently, a liquid immersion lithography method has been reported, whichpurports to address some of the issues facing the industry. By employingliquid immersion lithography, a resist pattern having a higherresolution and an excellent depth of focus can be formed at a low cost,using a lens mounted on existing exposure systems, such that the liquidimmersion lithography has attracted considerable attention.

As a result of moving to immersion lithography and multi-patterning, theneed exists for a new class of conformally deposited materials to bedeposited on top of photo resist, BARC, and other traditional maskinglayers. This new conformal deposition layer can serve 2 major functions:

-   -   1) It can act as a transparent protection layer (or “mask”) to        prevent chemical attack by the immersion lithography fluid. In        this case, the conformal layer needs to be transparent, and be        able to integrate with the lithography process without adverse        patterning and exposure issues.    -   2) It can have a higher etch selectivity than prior art and        traditional films such as amorphous carbon (which become more        opaque with increasing thickness). For example, multi-patterning        processes may require thicker (>10,000 A), and therefore more        opaque, amorphous carbon layers in order to achieve the        necessary etch protection. To achieve a similar etch resistance,        metal oxide conformal films can remain transparent while        maintaining the required etch selectivity during the plasma etch        process.

High purity of the reactant gases used in these processes are required,in order to ensure consistent chemical makeup for smoothness, etch anddeposition characteristics, 100% step coverage/conformality requirement.

The purity of the film produced is also required to be high, due to theuse of the film as a resist protection layer during etch or during lithoimmersion processing. Impurities in the film can have adverse reactions,chemically or optically, which interfere with the pattern quality andwhich can affect critical dimensions on the device features as well asthese impurities leaching into or contaminating adjacent layers, whichcan result in degradation of the integrated device performance.

Conventional resist compositions cannot always be used in liquidimmersion lithography processes, for a variety of reasons. For example,in the liquid immersion lithography process, the resist film is directlyin contact with the refractive index liquid (immersion liquid) duringthe exposure, and hence the resist film is vulnerable to attack by theliquid. Resist compositions suitable for use in liquid immersionlithography processes must also be transparent to the exposure light.Further, conventional resist compositions may not be able to achieve asatisfactory resolution of pattern in liquid immersion lithography dueto a change in their properties by the liquid, despite their utility inlithography employing the exposure through a layer of air.

Thus, there remains a need for improved transparent resist protectionlayers which can meet the increased requirements of the industry.Further, higher selectivity ALD films are needed for multi-patterning,as outlined above.

SUMMARY

Disclosed herein are compounds useful for the deposition of high puritytin oxide. Films deposited using such compounds demonstrate highconformality, high etch selectivity, high hardness and modulus, and areoptically transparent.

Compounds include those of Formula I, below:R_(x)—Sn-A_(4-x)  Formula Iwherein:

-   -   A is selected from the group consisting of (Y_(a)R′_(z)) and a        3- to 7-membered N-containing heterocyclic group;    -   each R group is independently selected from the group consisting        of an alkyl or aryl group having from 1 to 10 carbon atoms;    -   each R′ group is independently selected from the group        consisting of an alkyl, acyl or aryl group having from 1 to 10        carbon atoms;    -   x is an integer from 0 to 4;    -   a is an integer from 0 to 1;    -   Y is selected from the group consisting of N, O, S, and P; and    -   z is 1 when Y is O, S or when Y is absent and z is 2 when Y is N        or P

The use of compounds of Formula I allows for chemical vapour deposition(CVD) and atomic layer deposition (ALD) of tin oxide at a lowtemperature, and produces films consisting of high purity tin oxidehaving low metallic impurities, high hardness and modulus, and >99% stepcoverage (i.e. high conformality) over device features and topography.

Also disclosed is the purification of compounds of Formula I bymultistage distillation. Such purification yields so-called “ultra-pure”compounds having higher assay purity and much lower levels of metallicimpurities compared to compounds purified by conventional means. The useof such ultra-pure compounds in the processes disclosed herein resultsin films having improved properties compared to those known in the art.For example, the films may have improved hermetic properties, lowimpurities and improvements in the associated yield loss and long termreliability failures resulting from such impurities. Multistagedistillation may be carried out in the form of packed columns, stagedistillation columns employing trays, multiple distillation columns, orother types of multistage distillation.

The tin oxide film so produced may also exhibit high etch selectivityverses traditional masking and conformal layers used in multilayerpatterning integration techniques, resulting in a thinner filmrequirement as compared to traditional films such as amorphous carbon,boron doped carbon, etc.

In an embodiment, in the organometallic compound of Formula I, A isselected from the group consisting of an (NR′2) group and a 3- to7-membered N-containing heterocyclic group. In an embodiment, A is an(NR′2) group. In an embodiment, A is a 3- to 7-membered N-containingheterocyclic group. In an embodiment, A is a pyrrolidinyl group. In anembodiment, A_(4-x) is (NMe₂)₂ or (NEtMe)₂.

In other embodiments R and R′ group is an independently selected alkylgroup having from 1 to 10 carbon atoms. It is contemplated that each Rand R′ group may be an independently selected alkyl group having from 1to 6 carbon atoms. In embodiments, each R and R′ group is anindependently selected alkyl group having from 1 to 4 carbon atoms. Inembodiments, R and R′ is independently selected from the groupconsisting of methyl, ethyl, propyl, iso-propyl, tert-butyl, iso-butyland n-butyl. In embodiments R and R′ represent different alkyl groups.

In an embodiment, the compound of Formula I is selected from the groupconsisting of Me₂Sn(NMe₂)₂, Me₂Sn(NEtMe)₂, t-BuSn(NEtMe)₃,i-PrSn(NEtMe)₃, n-Pr(NEtMe)₃, EtSN(NEtMe)₃, i-BuSn(NEtMe)₃,Et₂Sn(NEtMe)₂, Me₂Sn(NEtMe)₂, Sn(NEtMe)₄, Bu₂Sn(NEtMe)₂, Et₂Sn(NMe₂)₂,Me₂Sn(NEt₂)₂, Sn(Pyrrolidinyl)₄ and Bu₂Sn(Pyrrolidinyl)₂.

In embodiments, the compound of Formula I is selected from the groupconsisting of Me₂Sn(NMe₂)₂, Me₂Sn(NEtMe)₂, Et₂Sn(NMe₂)₂, Me₂Sn(NEt₂)₂,Sn(Pyrrolidinyl)₄; and Bu₂Sn(Pyrrolidinyl)₂.

In embodiments, the compound of Formula I is selected from the groupconsisting of Me₂Sn(NEtMe)₂ and Me₂Sn(NMe₂)₂.

In embodiments, the compound of Formula I is Me₂Sn(NMe₂)₂.

In embodiments, a composition is provided that comprises theorganometallic compound of any of the disclosed compounds and anotherorganometallic compound containing Sn. The another organometalliccompound may be a compound of Formula I.

In various embodiments, another organometallic compound is selected fromthe group consisting of MeSn(NMe₂)₃ and Sn(NMe₂)₄.

In an embodiment, a method of using multistage distillation to purifythe organometallic compounds disclosed. In an embodiment, 2 to 20 stagesare required to reduce metal contamination to <1 ppm. In an embodiment,2 to 20 stages are required to reduce metal contamination to <100 ppb.In an embodiment, 2 to 20 stages are required to reduce metalcontamination to <10 ppb. In an embodiment, 2 to 20 stages are requiredto reduce metal contamination to 1 ppb or less.

The foregoing and other features of the invention and advantages of thepresent invention will become more apparent in light of the followingdetailed description of the preferred embodiments, as illustrated in theaccompanying figures. As will be realized, the invention is capable ofmodifications in various respects, all without departing from theinvention. Accordingly, the drawings and the description are to beregarded as illustrative in nature, and not as restrictive

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows the NMR spectrum of Me₃SnNMe₂.

FIG. 2 shows the NMR spectrum of Sn(NMe₂)₄.

FIG. 3 shows the NMR spectrum of Me₂Sn(NEtMe)₂.

FIG. 4 shows the NMR spectrum of Bu₂Sn(NMe₂)₂.

FIG. 5 shows the NMR spectrum of Me₂SnEt₂.

FIG. 6 shows the NMR spectrum of Me₄Sn.

FIG. 7 shows the NMR spectrum of Bu₂Sn(OMe)₂.

FIG. 8 shows the NMR spectrum of Bu₂Sn(OAc)₂.

FIG. 9 shows the NMR spectrum of Et₂Sn(NMe₂)₂.

FIG. 10 shows the NMR spectrum of Me₂Sn(NEt₂)₂.

FIG. 11 shows the NMR spectrum of Sn(Pyrrolodinyl)₄.

FIG. 12 shows the NMR spectrum of Bu₂Sn(Pyrrolodinyl)₂.

FIG. 13 shows the NMR spectrum of Et₂Sn(Pyrrolodinyl)₂.

FIG. 14 shows the NMR spectrum of Me₂Sn(NMe₂)₂.

FIG. 15 shows the NMR spectrum of tBuSn(NMe₂)₃.

FIG. 16 shows the NMR of the reaction of (NMe₂)₄Sn with ethanol.

FIG. 17 shows the NMR of the reaction of Me₃SnNMe₂ with water.

FIG. 18 shows the NMR of the reaction of Bu₂Sn(OAc)₂ with methanol.

FIG. 19 shows the NMR of the reaction of Bu₂Sn(OMe)₂ with acetic acid.

FIG. 20 shows the NMR of the reaction of Bu₂Sn(NMe₂)₂ with methanol.

FIG. 21 shows the NMR of Me₄Sn before and after heating at 200° C.

FIG. 22 shows the NMR of Et₂Sn(NMe₂)₂ before and after heating at 200°C.

FIG. 23 shows the NMR of Me₂Sn(NMe₂)₂ before and after heating at 150°C.

FIG. 24 shows the decomposition temperatures of illustrative compoundsof Formula I.

FIG. 25 shows a schematic of a multistage distillation apparatus.

DETAILED DESCRIPTION OF PARTICULAR EMBODIMENTS

Disclosed are organometallic compounds of Formula I, below:R_(x)—Sn-A_(4-x)  Formula Iwherein:

-   -   A is selected from the group consisting of (Y_(a)R′_(z)) and a        3- to 7-membered N-containing heterocyclic group;    -   each R group is independently selected from the group consisting        of an alkyl or aryl group having from 1 to 10 carbon atoms;    -   each R′ group is independently selected from the group        consisting of an alkyl, acyl or aryl group having from 1 to 10        carbon atoms;    -   x is an integer from 0 to 4;    -   a is an integer from 0 to 1;    -   Y is selected from the group consisting of N, O, S, and P; and    -   z is 1 when Y is O, S or when Y is absent and z is 2 when Y is N        or P

Compounds of Formula I include those in which R is selected from thegroup consisting of alkyl and aryl groups having from 1 to 10 carbonatoms. Particular compounds are those in which R is selected from thegroup consisting of alkyl and aryl groups having from 1 to 6 carbonatoms. More particular are those in which R is selected from the groupconsisting of alkyl and aryl groups having from 1 to 4 carbon atoms.Examples of such compounds include those in which R is a methyl, ethylor a butyl group.

Compounds of Formula I include those in which R′ is selected from thegroup consisting of alkyl, acyl and aryl groups having from 1 to 10carbon atoms. Particular compounds are those in which R′ is selectedfrom the group consisting of alkyl, acyl and aryl groups having from 1to 6 carbon atoms. More particular are those in which R′ is selectedfrom the group consisting of alkyl, acyl and aryl groups having from 1to 4 carbon atoms. Examples of such compounds include those in which R′is a methyl group, an ethyl group or an acetyl group.

Compounds of Formula I include those in which Y is selected from thegroup consisting of N, O, S, and P. Particular compounds are those inwhich Y is selected from the group consisting of N and O.

Compounds of Formula I include those in which x is an integer from 0 to4. In particular embodiments, x is an integer from 1 to 3. Morepreferably, x is 2.

Compounds of Formula I include those in which A is a 3- to 7-memberedN-containing heterocyclic group such as aziridinyl, pyrrolidinyl, andpiperidinyl. Particular compounds are those in which A is a pyrrolidinylor piperidinyl group.

Compounds of Formula I include those in which R is an alkyl group and Ais an NR′₂ group, and wherein R′ is an alkyl group. Particular compoundsare those in which R and R′ represent different alkyl groups.

Compounds of Formula I are thermally stable whilst exhibiting goodreactivity. Thus, delivery of the compound to the deposition chamberwill take place without decomposition occurring. (decomposition resultsin a deposited film which will not be uniform). A good stability andreactivity profile, as demonstrated by the compounds of the invention,also means that less material is required to be delivered to the growthchamber (less material is more economic), and cycling will be faster (asthere will be less material left in the chamber at the end of theprocess to be pumped oft), meaning that thicker films can be depositedin shorter times, so increasing throughput. Further, ALD can be carriedout at much lower temperatures (or using a wider temperature window)using compounds of Formula I than processes of the art. Thermalstability also means that material can be purified much more easilyafter synthesis, and handling becomes easier.

Such compounds are useful for encapsulating and protecting the resistlayers used in liquid immersion lithography (i.e. acting as a “mask”).Thus, the compounds disclosed herein may be used for the manufacture ofa transparent tin oxide film having properties suitable for depositionover photoresists, or other organic masking layers, to allow forprotection of the underlying layer during liquid immersion lithography,and which permits the manufacture of devices having improvedsemiconductor device performance such as low defect density, improveddevice reliability, high device density, high yield, good signalintegrity and suitable power delivery, as required by the industry.

Further, the use of a compound of Formula I in the methods disclosedherein allows for chemical vapour deposition (CVD) and atomic layerdeposition (ALD) of tin oxide at a low temperature, and produces filmsconsisting of high purity tin oxide having low metallic impurities,and >99% step coverage (i.e. high comformality) over device features andtopography.

Compounds of Formula I may be prepared by processes known in the art.The examples below are illustrative of such processes, but are notintended to be limiting.

Example 1: Synthesis of Me₃Sn(NMe₂)

In a 250 mL flask was charged 20 mL of 2.5M Butyllithium solution inhexane and 50 mL of anhydrous hexane. To the solution, Me₂NH gas waspassed till fully reacted and the reaction mixture was stirred for 2hrs. The solution of 10 g of Me₃SnCl in 100 mL of anhydrous hexane wasthen added and the mixture was stirred for 12 hrs. Filtration wascarried out to remove solid. The solvent was removed under reducedpressure. The liquid product was purified by distillation under reducedpressure. NMR confirmed the product to be Me₃SnNMe₂, as shown in FIG. 1.

Example 2: Synthesis of Sn(NMe₂)₄

In a 250 mL flask was charged 80 mL of 2.5M Butyllithium solution inhexane and 50 mL of anhydrous hexane. To the solution, Me₂NH gas waspassed till fully reacted and the reaction mixture was stirred for 2hrs. The solution of 13 g of SnCl₄ in 100 mL of anhydrous benzene wasthen added and the mixture was refluxed for 4 hrs. Once cooled,filtration was carried out to remove solid. The solvent was removedunder reduced pressure. The liquid product was purified by distillationunder reduced pressure. NMR confirmed the product to be Sn(NMe₂)₄, asshown in FIG. 2 .

Example 3: Synthesis of Me₂Sn(NEtMe)₂

Under inert atmosphere, a 1 L round bottom flask was charged with 25.00mL of 2.5M Butyllithium solution in hexane and 200 mL of anhydroushexane, followed by a slow addition of 5.40 mL of HNEtMe in 100 mL ofanhydrous hexane. The reaction mixture was then stirred at roomtemperature for 1 h. The solution of 6.70 g of Me₂SnCl₂ in 200 mL ofanhydrous benzene was then added to the flask (while cooled in the icebath), and the reaction mixture was left stirring at room temperatureovernight. The solvent was removed under reduced pressure from thefiltrate. The liquid product was isolated by distillation under reducedpressure (80° C. at 9.8×10⁻² Torr). As shown in FIG. 3 , the product wasconfirmed to be Me₂Sn(NEtMe)₂ by NMR spectroscopy.1) nBuLi+HNEtMe→LiNEtMe+butane  Formula II2) Me₂SnCl₂+2LiNEtMe→Me₂Sn(NEtMe)₂+2LiCl  Formula III

Example 4: Synthesis of Bu₂Sn(NMe₂)₂

In a 250 mL flask was charged 24 mL of 2.5M Butyllithium solution inhexane and 100 mL of anhydrous hexane. To the solution, Me₂NH gas waspassed till fully reacted and the reaction mixture was stirred for 2hrs. The solution of 9.11 g of Bu₂SnCl₂ in 100 mL of anhydrous benzenewas then added and the mixture was stirred for 4 hrs. Filtration wascarried out to remove solid. The solvent was removed under reducedpressure. The liquid product was purified by distillation under reducedpressure. NMR confirmed the product to be Bu₂Sn(NMe₂)₂, as shown in FIG.4 .

Example 5: Synthesis of Me₂SnEt₂

6.59 g of Me₂SnCl₂ was dissolved in 100 mL of anhydrous ether, followedby the addition of 30 mL of 3M EtMgBr under N₂. After stirring for 4hrs, mixture was treated with 0.1M HCl solution and organic layer wascollected. The collected organic layer was then treated with saturatedNaHCO₃ solution and organic layer is collected. Distillation under N₂was carried out to remove ether. Purification was carried out bydistillation under reduced pressure. As shown in FIG. 5 , NMR confirmedthe product to be Me₂SnEt₂.

Example 6: Synthesis of Me₄Sn

To the solution of 23.5 g of SnCl₄ in ether was added 150 mL of 3M MeMgIunder N₂. After stirring for 4 hrs, mixture was treated with 0.1 M HClsolution and organic layer was collected. The collected organic layerwas then treated with saturated NaHCO₃ solution and organic layer iscollected. Fractional distillation was carried out to remove ether.Purification was carried out by distillation under reduced pressure. Asshown in FIG. 6 , NMR confirmed the product to be Me₄Sn.

Example 7: Synthesis of Bu₂Sn(OMe)₂

To a 250 mL flask was charged 20 g of Bu₂SnCl₂ and 20 mL of anhydrousmethanol, followed by the addition of 7 g of sodium methoxide in 30 mLof anhydrous methanol. The resulting mixture was refluxed for 12 hrs.Filtration was carried out to remove solid. The solvent was removedunder reduced pressure. The liquid product was purified by distillationunder reduced pressure. As shown in FIG. 7 , NMR confirmed the productto be Bu₂Sn(OMe)₂.

Example 8: Synthesis of Bu₂Sn(OAc)₂

Sodium acetate was first made by adding 6 g acetic acid into a solutionof 5.4 g of sodium methoxide in 30 mL of anhydrous methanol. This wasthen added into the mixture of 30 g of Bu₂SnCl₂ in 30 mL of anhydrousmethanol. The resulting mixture was refluxed for 4 hrs. Filtration wascarried out to remove solid. The solvent was removed under reducedpressure. The liquid product was purified by distillation under reducedpressure. As shown in FIG. 8 , NMR confirmed the product to beBu₂Sn(OAc)₂.

Example 9: Synthesis of Et₂Sn(NMe₂)₂

A 1 L flask was charged with 22 mL of 2.5M Butyllithium solution inhexane and 400 mL of anhydrous hexane. Me₂NH gas was passed through thesolution, and the reaction mixture was stirred for 1 h. The solution of6.71 g of Et₂SnCl₂ in 100 mL of anhydrous benzene was then added and themixture was stirred for 4 hrs. Filtration was carried out to remove anysolid products. The solvent was removed under reduced pressure from thefiltrate. The liquid product was purified by distillation under reducedpressure. As shown in FIG. 9 , NMR confirmed the product to beEt₂Sn(NMe₂)₂.

Example 10: Synthesis of Me₂Sn(NEt₂)₂

In a 250 mL flask was charged 24 mL of 2.5M Butyllithium solution inhexane and 50 mL of anhydrous hexane, followed by the addition of 4.39 gof Et₂NH. The reaction mixture was stirred for 2 hrs. The solution of6.59 g of Me₂SnCl₂ in 100 mL of anhydrous ether was then added and themixture was stirred for 4 hrs. Filtration was carried out to removesolid. The solvent was removed under reduced pressure. The liquidproduct was purified by distillation under reduced pressure. As shown inFIG. 10 , NMR confirmed the product to be Me₂Sn(NEt₂)₂.

Example 11: Synthesis of Sn(Pyrrolidinyl)₄

Under inert atmosphere, a 100 mL round bottom flask was charged with 0.5mL of Sn(NMe₂)₄ and 25 mL of anhydrous hexane, followed by a drop-wiseaddition of 1.1 mL of pyrrolidene. After stirring the reaction mixtureat room temperature for 2 h, the solvent was removed via distillationunder reduced pressure. The residue remaining in the reaction flask wasconfirmed to be Sn(Pyrrolodinyl)₄ by NMR spectroscopy, as shown in FIG.11 .

Example 12: Synthesis of Bu₂Sn(Pyrrolodinyl)₂

Under inert atmosphere, a 1 L round bottom flask was charged with 25 mLof 2.5M Butyllithium solution in hexane and 200 mL of anhydrous hexane,followed by a slow addition of 5.3 mL of pyrrolidene in 25 mL ofanhydrous hexane. The reaction mixture was then stirred at roomtemperature for 1 h, and then placed into the ice bath. The solution of9.46 g of Bu₂SnCl₂ in 50 mL of anhydrous hexane was then added to theflask, and the reaction mixture was left stirring at room temperaturefor 2 h. Filtration was carried out to remove any solid products. Thesolvent was removed under reduced pressure from the filtrate. As shownin FIG. 12 , the product was confirmed to be Bu₂Sn(Pyrrolodinyl)₂ by NMRspectroscopy.

Example 13: Synthesis of Et₂Sn(Pyrrolodinyl)₂

Under inert atmosphere, a 1 L round bottom flask was charged with 5.3 mLof pyrrolidene and 200 mL of anhydrous pentane. Once the reaction flaskwas placed in the ice bath, 25 mL of 2.5M Butyllithium solution inhexane were slowly added to the reaction flask while stirringvigorously. The reaction mixture was then stirred at room temperaturefor 1 h, and then placed back into the ice bath. The solution of 7.7 gof Et₂SnCl₂ in 100 mL of anhydrous pentane and 20 mL of anhydrousbenzene was then added to the flask, and the reaction mixture was leftstirring at room temperature overnight. Filtration was carried out toremove any solid products. The solvent was removed under reducedpressure from the filtrate. Final product was purified via vacuumdistillation. As shown in FIG. 13 , the product is confirmed to beEt₂Sn(Pyrrolodinyl)₂ by NMR spectroscopy.

Example 14: Synthesis of Me₂Sn(NMe₂)₂

Under inert atmosphere, a 1 L flask was charged with 25 mL of 2.5MButyllithium solution in hexane and 400 mL of anhydrous hexane. Thereaction flask was placed in the ice bath and Me₂NH gas was passedthrough the solution until a white slushy solution was obtained (ca. 15min). Afterwards the reaction mixture was stirred for 1 h at roomtemperature. The reaction flask was placed in the ice bath again and thesolution of 6.7 g of Me₂SnCl₂ in 100 mL of anhydrous benzene was slowlyadded, and the mixture was stirred overnight at room temperature.Filtration was carried out to remove any solid products. The solvent wasremoved under reduced pressure from the filtrate. The liquid product waspurified by distillation under reduced pressure. As shown in FIG. 14 ,the product is confirmed to be Me₂Sn(NMe₂)₂ by NMR spectroscopy.

Example 15: Synthesis of tBuSn(NMe₂)₃

Sn(NMe₂)₄ +tBuLi→tBuSn(NMe₂)₃+LiNMe₂  Formula IV

Under inert atmosphere, a 5 L round bottom flask was charged with 100 mLof Sn(NMe₂)₄ and ca. 3 L of anhydrous hexane. The mixture was stirredusing a mechanical stirrer, and placed in the ethylene-glycol bath at−15° C. In the glovebox, a 1 L flask was loaded with 200 mL of 1.7Mtert-butyllithium solution in anhydrous hexane, and ca. 200 mL ofanhydrous hexane. The tBuLi solution was then slowly added to thereaction flask. The reaction mixture was stirred at room temperature for3 h. The stirring was then stopped, and salts were left to precipitateout of the reaction mixture overnight. The liquid was cannulated intoanother 5 L round bottom flask. The solvents were removed viadistillation, and 62 g of the final product were isolated bydistillation under reduced pressure (120° C., 6.2×10⁻² Torr). As shownin FIG. 15 , the product was confirmed to be tBuSn(NMe₂)₃ by NMRspectroscopy. 90% tBuSn(NMe₂)₃ and 10% tBu₂Sn(NMe₂)₂.

Similarly, complexes of the type RSn(NEtMe)₃ can be synthesizedfollowing the above procedure by reacting Sn(NEtMe)₄ with RLi, whereR=Et, iPr, iBu, nPrSn(NEtMe)₄+RLi→RSn(NEtMe)₃+LiNEtMe  Formula V

-   -   where R=Et, iPr, iBu, nPr

Example 16: Sn(NEtMe)₄+EtLi→EtSn(NEtMe)₃+LiNEtMe

Under inert atmosphere, a 5 L round bottom flask was charged with 100 gof Sn(NEtMe)₄ and ca. 2.5 L of anhydrous hexane. The mixture was stirredusing a mechanical stirrer, and placed in the ethylene-glycol bath at−15° C. In the glovebox, a 1 L flask was loaded with 655 mL of 0.5 Methyllithium solution in anhydrous benzene, and ca. 200 mL of anhydrousbenzene. The EtLi solution was then slowly added to the reaction flask.The reaction mixture was stirred at room temperature for 3 h. Thestirring was then stopped, and salts were left to precipitate out of thereaction mixture overnight. The liquid was cannulated into another 5 Lround bottom flask. The solvents were removed via distillation, and thefinal product isolated via distillation under reduced pressure.

Example 17: Sn(NEtMe)₄+iPrLi→iPrSn(NEtMe)₃+LiNEtMe

Under inert atmosphere, a 5 L round bottom flask was charged with 100 gof Sn(NEtMe)₄ and ca. 2.5 L of anhydrous hexane. The mixture was stirredusing a mechanical stirrer, and placed in the ethylene-glycol bath at−15° C. In the glovebox, a 1 L flask was loaded with 468 mL of 0.7 Misopropyllithium solution in anhydrous pentane, and ca. 200 mL ofanhydrous hexane. The iPrLi solution was then slowly added to thereaction flask. The reaction mixture was stirred at room temperature for3 h. The stirring was then stopped, and salts were left to precipitateout of the reaction mixture overnight. The liquid was cannulated intoanother 5 L round bottom flask. The solvents were removed viadistillation, and the final product isolated via distillation underreduced pressure.

Example 18: Sn(NEtMe)₄+iBuLi→iBuSn(NEtMe)₃+LiNEtMe

Under inert atmosphere, a 5 L round bottom flask was charged with 100 gof Sn(NEtMe)₄ and ca. 3 L of anhydrous hexane. The mixture was stirredusing a mechanical stirrer, and placed in the ethylene-glycol bath at−15° C. In the glovebox, a 1 L flask was loaded with 193 mL of 1.7 Misobutyllithium solution in anhydrous heptane, and ca. 200 mL ofanhydrous hexane. The iBuLi solution was then slowly added to thereaction flask. The reaction mixture was stirred at room temperature for3 h. The stirring was then stopped, and salts were left to precipitateout of the reaction mixture overnight. The liquid was cannulated intoanother 5 L round bottom flask. The solvents were removed viadistillation, and the final product isolated via distillation underreduced pressure.

Example 19: Sn(NEtMe)₄+nPrLi→nPrSn(NEtMe)₃+LiNEtMe

Under inert atmosphere, a 5 L round bottom flask was charged with 100 gof Sn(NEtMe)₄ and ca. 3 L of anhydrous hexane. The mixture was stirredusing a mechanical stirrer, and placed in the ethylene-glycol bath at−15° C. In the glovebox, a 1 L flask was loaded with 193 mL of 1.7 Mn-propyllithium solution in anhydrous heptane, and ca. 200 mL ofanhydrous hexane. The nPrLi solution was then slowly added to thereaction flask. The reaction mixture was stirred at room temperature for3 h. The stirring was then stopped, and salts were left to precipitateout of the reaction mixture overnight. The liquid was cannulated intoanother 5 L round bottom flask. The solvents were removed viadistillation, and the final product isolated via distillation underreduced pressure.

Example 20: Comparative Reactivity Tests

a)

-   -   To Sn(NMe₂)₄ was added water. Reaction took place spontaneously.        The clear Sn(NMe₂)₄ turned cloudy and a white solid formed.    -   To Sn(NMe₂)₄ was added anhydrous ethanol. The mixture warmed up        and NMR confirmed the complete replacement of —NMe₂ group by        —OEt group. More ethanol was added and NMR was carried out to        further confirm the completion of the reaction (FIG. 16 ).        b)    -   To Me₃SnNMe₂ was added water. NMR indicated that no reaction        took place. The mixture was heated at 50° C. for 1 hr. NMR        showed that reaction took place (FIG. 17 ).    -   To Me₃SnNMe₂ was added anhydrous methanol NMR indicated that no        reaction took place. The mixture was heated at 50° C. for 1 hr.        The clear solution turned cloudy. NMR confirmed that reaction        had taken place.        c)    -   To Bu₂Sn(OAc)₂ was added water. Reaction took place        spontaneously. The clear Bu₂Sn(OAc)₂ turned cloudy and a white        solid formed.    -   To Bu₂Sn(OAc)₂ was added anhydrous methanol. NMR showed that no        reaction took place (FIG. 18 ).        d)    -   To Bu₂Sn(OMe)₂ was added water. Reaction took place        spontaneously. The clear Bu₂Sn(OMe)₂ turned cloudy and a white        solid formed.    -   To Bu₂Sn(OMe)₂ was added acetic acid. NMR shows that some —OMe        group has been replaced by —OAc group (FIG. 19 ).        e)    -   To Bu₂Sn(NMe₂)₂ was added water. Reaction took place        spontaneously. The clear Bu₂Sn(NMe₂)₂ turned cloudy and a white        solid formed.    -   To Bu₂Sn(NMe₂)₂ was added Methanol. NMR shows that some —NMe₂        group has been replaced by —OMe group (FIG. 20 ).

Example 21: Thermal Stability Tests

Thermal stability tests of compounds of Formula I were carried out insealed glass ampoules, which were heated at a set temperature for 1 hr.NMR was performed to see if there had been any thermal decomposition. Avisual check was also used, looking for solid formation after heattreatment. FIG. 21 shows NMR of Me₄Sn before and after heating at 200°C. There was no significant change after heating at 200° C. for 1 hrbased on both NMR and visual check.

FIG. 22 shows NMR of Et₂Sn(NMe₂)₂ before and after heating at 200° C.There was no significant change after heating at 200° C. for 1 hr basedon both NMR and visual check.

FIG. 23 shows NMR of Me₂Sn(NMe₂)₂ before and after heating at 150° C.There was no significant change after heating at 150° C. for 24 hr basedon both NMR and visual check.

FIG. 24 shows the decomposition temperature of representative compoundsof Formula I.

These results demonstrate that compounds of Formula I are thermallystable, showing that delivery of the compound to the deposition chamberwill take place without observable decomposition occurring.

Multistage Distillation

Various forms of multistage distillation are known in the chemicalmanufacturing industry, but have not been employed for the purificationof organometallic materials that include tetramethyl tin or othercompounds of Formula I.

As illustrated by the schematic shown in FIG. 25 , multiple-effect ormultistage distillation (MED) is a distillation process often used forsea water desalination. It consists of multiple stages or “effects”. (Inschematic in FIG. 25 the first stage is at the top. Pink areas arevapor, lighter blue areas are liquid feed material. The turquoiserepresents condensate. It is not shown how feed material enters otherstages than the first, however those should be readily understood.F—feed in. S—heating steam in. C—heating steam out. W—purified material(condensate) out. R—waste material out. O—coolant in. P—coolant out. VCis the last-stage cooler.) In each stage the feed material is heated bysteam in tubes. Some of the feed material evaporates, and this steamflows into the tubes of the next stage, heating and evaporating more ofthe distillate. Each stage essentially reuses the energy from theprevious stage.

The plant can be seen as a sequence of closed spaces separated by tubewalls, with a heat source at one end and a heat sink at the other. Eachspace consists of two communicating subspaces, the exterior of the tubesof stage n and the interior of the tubes in stage n+1. Each space has alower temperature and pressure than the previous space, and the tubewalls have intermediate temperatures between the temperatures of thefluids on each side. The pressure in a space cannot be in equilibriumwith the temperatures of the walls of both subspaces; it has anintermediate pressure. As a result, the pressure is too low or thetemperature too high in the first subspace, and the feed materialevaporates. In the second subspace, the pressure is too high or thetemperature too low, and the vapor condenses. This carries evaporationenergy from the warmer first subspace to the colder second subspace. Atthe second subspace the energy flows by conduction through the tubewalls to the colder next space.

As shown by Table 2 below, purification of SnMe₄ by multistagedistillation results in a compound having significantly lower levels ofimpurities compared to that purified by conventional means.

TABLE 2 Single Single Average Delta Multi stage stage single vs SingleMultistage option 1 option 2 stage ppb % Element ppb ppb ppb ppbdifference Ag 5 10 5 7.5 −33% Al 5 40 20 30 −83% As 50 50 100 75 −33% Au10 10 5 7.5  33% B 40 70 10 40  0% Be 1 1 5 3 −67% Bi 1 2 5 3.5 −71% Ca80 270 100 185 −57% Cd 1 1 5 3 −67% Co 0 1 5 3 −100%  Cr 2 3 5 4 −50% Cu4 12 5 8.5 −53% Fe 11 31 10 20.5 −46% Hf 0 0 5 2.5 −100%  K 30 30 20 25 20% Li 2 5 50 27.5 −93% Mg 8 35 50 42.5 −81% Mn 0.5 0.5 5 2.75 −82% Mo0.5 1.8 5 3.4 −85% Na 200 200 100 150  33% Nb 0.5 0.5 5 2.75 −82% N 150150 5 77.5  94% Pb 0.4 2.1 2 2.05 −80% Pd 0.5 0.5 5 2.75 −82% Pt 2 2 53.5 −43% Rb 1 1 5 3 −67% Re 0.5 0.5 5 2.75 −82% Rh 0.5 0.5 5 2.75 −82%Ru 0.5 0.5 5 2.75 −82% Sb 20 120 250 185 −89%

The use of the terms “a” and “an” and “the” and similar referents in thecontext of describing the invention (especially in the context of thefollowing claims) are to be construed to cover both the singular and theplural, unless otherwise indicated herein or clearly contradicted bycontext. The terms “comprising,” “having,” “including,” and “containing”are to be construed as open-ended terms (i.e., meaning “including, butnot limited to,”) unless otherwise noted. The term “connected” is to beconstrued as partly or wholly contained within, attached to, or joinedtogether, even if there is something intervening.

The recitation of ranges of values herein are merely intended to serveas a shorthand method of referring individually to each separate valuefalling within the range, unless otherwise indicated herein, and eachseparate value is incorporated into the specification as if it wereindividually recited herein.

All methods described herein can be performed in any suitable orderunless otherwise indicated herein or otherwise clearly contradicted bycontext. The use of any and all examples, or exemplary language (e.g.,“such as”) provided herein, is intended merely to better illuminateembodiments of the invention and does not impose a limitation on thescope of the invention unless otherwise claimed. The various embodimentsand elements can be interchanged or combined in any suitable manner asnecessary.

No language in the specification should be construed as indicating anynon-claimed element as essential to the practice of the invention.

It will be apparent to those skilled in the art that variousmodifications and variations can be made to the present inventionwithout departing from the spirit and scope of the invention. There isno intention to limit the invention to the specific form or formsdisclosed, but on the contrary, the intention is to cover allmodifications, alternative constructions, and equivalents falling withinthe spirit and scope of the invention, as defined in the appendedclaims. Thus, it is intended that the present invention cover themodifications and variations of this invention provided they come withinthe scope of the appended claims and their equivalents.

The invention claimed is:
 1. A method purifying an organometalliccompound comprising: A) distilling in a first stage an organometalliccompound of Formula 1:R_(x)—Sn-A_(4-x)  Formula I wherein: each R group is independentlyselected from the group consisting of an alkyl group having from 1 to 10carbon atoms; each R′ group is independently selected from the groupconsisting of an alkyl group having from 1 to 10 carbon atoms; x is aninteger from 0 to 3; wherein distilling in the first stage includes: i)feeding feed material containing the first organometallic compound to afirst distillation space at a reduced first pressure, ii) heating thefirst distillation space to a first temperature to evaporate a portionof the feed material, and iii) removing the evaporated portion of thefeed material from the first distillation space such that a distillateis formed; B) distilling, in at least one subsequent stage, thedistillate from a previous stage, wherein distilling the distillate froma previous stage includes: i) feeding distillate from a previous stageto a subsequent distillation space at a reduced subsequent pressure, ii)heating the subsequent distillation space to a subsequent temperature toevaporate a portion of the distillate from a previous stage, iii)removing the evaporated portion of the distillate from a previous stagefrom the subsequent distillation space such that a subsequent distillateis formed; and C) removing a final distillate from last of thesubsequent stages, wherein step B is repeated a number of times at areduced subsequent pressure sufficient to obtain the final distillate ofthe organometallic compound having purity as measured by nuclearmagnetic resonance (NMR) spectroscopy of greater than 98%.
 2. The methodof claim 1, wherein step B is repeated 1 to 19 times.
 3. The method ofclaim 1, wherein, in each subsequent stage, the distillation space has asubsequent pressure that is lower than a subsequent pressure in aprevious stage.
 4. The method of claim 3, wherein, in each subsequentstage, a subsequent temperature is lower than a subsequent temperaturein a previous stage.
 5. The method of claim 1, wherein, in each stage,the heating step is by steam in tubes and, in each subsequent stage,steam in the tubes is the evaporated portion of the feed material ordistillate from a previous stage.
 6. The method of claim 1, wherein eachR group is an independently selected alkyl group having from 1 to 4carbon atoms.
 7. The method of claim 1, wherein each R′ group representsdifferent alkyl groups.
 8. The method of claim 1, wherein theorganometallic compound of Formula I is selected from the groupconsisting of Me₂Sn(NMe₂)₂, Me₂Sn(NEtMe)₂, t-BuSn(NEtMe)₃,t-BuSn(NMe₂)₃, t-BuSn(NEt₂)₃, i-PrSn(NEtMe)₃, i-PrSn(NEtMe₂)₃,n-PrSn(NEtMe)₃, n-PrSn(NEtMe₂)₃, EtSn(NEtMe)₃, i-BuSn(NEtMe)₃,i-BuSn(NEtMe₂)₃, n-BusSn(NMe₂)₃, sec-BuSn(NMe₂)₃, Et₂Sn(NEtMe)₂,Me₂Sn(NEtMe)₂, Sn(NMe₂)₄, Sn(NEt₂)₄, Sn(NEtMe)₄, Bu₂Sn(NEtMe)₂, andMe₂Sn(NEt₂)₂.
 9. The method of claim 8, wherein the organometalliccompound of Formula I is Sn(NMe₂)₄.
 10. The method of claim 1, whereinat least one of the reduced first pressure and the reduced subsequentpressure are less than 10⁻¹ torr.
 11. A method purifying anorganometallic compound comprising: A) distilling in a first stage anorganometallic compound of Formula 1:R_(x)-Sn-(NR′₂)_(4−x)  Formula I wherein: each R group is independentlyselected from the group consisting of an alkyl group having from 1 to 10carbon atoms; each R′ group is independently selected from the groupconsisting of an alkyl group having from 1 to 10 carbon atoms; x is aninteger from 0 to 3; wherein distilling in the first stage includes: i)feeding feed material containing the first organometallic compound to afirst distillation space at a reduced first pressure, ii) heating thefirst distillation space to a first temperature to evaporate a portionof the feed material, and iii) removing the evaporated portion of thefeed material from the first distillation space such that a distillateis formed; B) distilling, in at least one subsequent stage, thedistillate from a previous stage, wherein distilling the distillate froma previous stage includes: i) feeding distillate from a previous stageto a subsequent distillation space at a reduced subsequent pressure, ii)heating the subsequent distillation space to a subsequent temperature toevaporate a portion of the distillate from a previous stage, iii)removing the evaporated portion of the distillate from a previous stagefrom the subsequent distillation space such that a subsequent distillateis formed; and C) removing a final distillate from last of thesubsequent stages, wherein step B is repeated a number of times at areduced subsequent pressure sufficient to obtain the final distillate ofthe organometallic compound having a metal contamination of less than 1ppm.
 12. The method of claim 11, wherein step B is repeated a number oftimes sufficient to reduce metal contamination to less than 100ppb. 13.The method of claim 12, wherein step B is repeated a number of timessufficient to reduce metal contamination to 1ppb or less.
 14. The methodof claim 11, wherein step B is repeated 1 to 19 times.
 15. The method ofclaim 11, wherein, in each subsequent stage, the distillation space hasa subsequent pressure that is lower than a subsequent pressure in aprevious stage.
 16. The method of claim 15, wherein, in each subsequentstage, a subsequent temperature is lower than a subsequent temperaturein a previous stage.
 17. The method of claim 11, wherein, in each stage,the heating step is by steam in tubes and, in each subsequent stage,steam in the tubes is the evaporated portion of the feed material ordistillate from a previous stage.
 18. The method of claim 11, whereineach R′ group represents different alkyl groups.
 19. The method of claim11, wherein the organometallic compound of Formula I is selected fromthe group consisting of Me₂Sn(NMe₂)₂, Me₂Sn(NEtMe)₂, t-BuSn(NEtMe)₃,t-BuSn(NMe₂)₃, t-BuSn(NEt₂)₃, i-PrSn(NEtMe)₃, i-PrSn(NEtMe₂)₃,n-PrSn(NEtMe)₃, n-PrSn(NEtMe₂)₃, EtSn(NEtMe)₃, i-BuSn(NEtMe)₃,i-BuSn(NEtMe₂)₃, n-BusSn(NMe₂)₃, sec-BuSn(NMe₂)₃, Et₂Sn(NEtMe)₂,Me₂Sn(NEtMe)₂, Sn(NMe₂)₄, Sn(NEt₂)₄, Sn(NEtMe)₄, Bu₂Sn(NEtMe)₂, andMe₂Sn(NEt₂)₂.
 20. The method of claim 19, wherein the organometalliccompound of Formula I is Sn(NMe₂)₄.
 21. The method of claim 11, whereinat least one of the reduced first pressure and the reduced subsequentpressure are less than 10⁻¹ torr.